Heat- and chemical-resistant resins typified by polybenzimidazole compounds are difficult to dissolve into solution and it is a common practice to mold the resins after being melted at elevated temperatures but this has limited the range of the applications with polybenzimidazole. Even if the resins are dissolved into special organic solvents, their solubility becomes low with the lapse of time due to association of polybenzimidazole molecule and other factors and, particularly in case that the concentration of the polybenzimidazole compounds is comparatively high, association of polybenzimidazole easily occurs and, as a matter of fact, the shelf life of the solution is very short, only ranging from several days to one or two weeks. In specialty applications, the shelf life of the solution can be extended by incorporating metal salts and other stabilizers into the solution, however, for most electronic devices, the incorporation of metallic components is not preferred since they will deteriorate the device characteristics significantly. In particular, the characteristics of semiconductor and display devices are greatly affected by metallic impurities and the use of the solutions of polybenzimidazole compounds has been very limited in these applications.
Under the circumstances, it has long been desired to develop polybenzimidazole compounds in solution that have comparatively long shelf lives without using stabilizers such as metal salts.